andywatson

I need to generate a precise 5v on my Arduino Uno board. I know the onboard regulator isn't very precise, and I've measured too much variation between the 5 different Uno boards I have. So how should I go about it? It seems like most precision voltage references need at least 6v so it can regulate it down to 5v. So do I need to use a DC-DC boost converter to boost the onboard Uno 5v up to something like 9v and then use a reference IC to generate the precise 5v?

Why not just get a switching 5V regulator? Then you won't see any variation.http://www.dipmicro.com/store/DCA-0510http://www.dipmicro.com/store/DCA-0520Or get 6V, 7.5V if you want to regulate it down yourself. Maybe use an LM317 with a trimming resistor (10 turn potentiometer) to get it right at 5v.

Standard approach to this is take a sufficiently accurate voltage reference chip (and maybe a precision op-amp to scale/buffer the output). Won't give a power supply but will be a voltage reference for an ADC for example.

If the application is analog->digital conversion there are many ADCs with built in references.

But without knowing the specification can't really suggest any concrete examples.

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andywatson

I need to power some pressure sensors that require a stable 5v excitation voltage. The sensor outputs an analog voltage that's proportional to pressure being exerted on the sensor. Currently I'm using the the ADC of the ATmega328 to sample the sensor output. Eventually I'll probably use a separate ADC chip because I want better than 10-bit resolution. Each sensor draws about 5ma, and I could have up to 5 sensors on one board. So if I could find an ADC chip that provided a 5v reference capable of supplying enough current and could read a voltage from 0 to 5v, then that would solve my problem.

andywatson

yes, but I'm using a precision 3.3v regulator as the external reference voltage for the Atmega328, so if the 5v excitation voltage varies, the output of the sensor compared to the stable 3.3v varies as well.

So use the 5V 1A switching regulator, will be a very stable 5V source for your 25mA plus the arduino's 30mA.Use the analog devices SPI ADC that's been posted previously with 6 sample & hold inputs & get 6 conversions at the same time.

andywatson

So use the 5V 1A switching regulator, will be a very stable 5V source for your 25mA plus the arduino's 30mA.Use the analog devices SPI ADC that's been posted previously with 6 sample & hold inputs & get 6 conversions at the same time.

Do you happen to know the part number of that ADC? I've been searching for days and haven't found one with 0-5v input and multiple channels.

Why not just get a switching 5V regulator? Then you won't see any variation.http://www.dipmicro.com/store/DCA-0510http://www.dipmicro.com/store/DCA-0520Or get 6V, 7.5V if you want to regulate it down yourself. Maybe use an LM317 with a trimming resistor (10 turn potentiometer) to get it right at 5v.

Hi,

I am having trouble with excessive time spent in the reflow zone of my sketch. Have tried manipulating zone temps & timings without success. I have come to the tentative conclusion that I need to regulate the 5v supply.

I am having trouble understanding how the power supply you recommend fits into the scheme of things, given that I need the usb power to run the Arduino Uno setup & monitor etc. You may want to view my OP topic: "Arduino code not giving target temperature" (in Project Guidance).

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yes, but I'm using a precision 3.3v regulator as the external reference voltage for the Atmega328, so if the 5v excitation voltage varies, the output of the sensor compared to the stable 3.3v varies as well.

You have not given the error rate of the pressure sensors. There is no reason to use a voltage source more precise than what you can expect from the sensors.